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Cell walls are crucial for the integrity and function of all land plants and are of central importance in human health, livestock production, and as a source of renewable bioenergy. Many enzymes that mediate the biosynthesis of cell wall polysaccharides are encoded by members of the large cellulose synthase (CesA) gene superfamily. Here, we analyzed 29 sequenced genomes and 17 transcriptomes to revise the phylogeny of the CesA gene superfamily in angiosperms. Our results identify ancestral gene clusters that predate the monocot-eudicot divergence and reveal several novel evolutionary observations, including the expansion of the Poaceae-specific cellulose synthase-like CslF family to the graminids and restiids and the characterization of a previously unreported eudicot lineage, CslM, that forms a reciprocally monophyletic eudicot-monocot grouping with the CslJ clade. The CslM lineage is widely distributed in eudicots, and the CslJ clade, which was thought previously to be restricted to the Poales, is widely distributed in monocots. Our analyses show that some members of the CslJ lineage, but not the newly identified CslM genes, are capable of directing (1,3;1,4)-𝛽-glucan biosynthesis, which, contrary to current dogma, is not restricted to Poaceae.

Main conclusion The changes in the expression of key sugar metabolism enzymes (SPS and SUS), sucrose content and arrangement of chloroplast starch may play a significant role in the cold response in M. giganteus  and maize plants. To understand the mechanism of the chilling-response of two closely-related C 4 plants, we investigated the changes in the expression of sucrose phosphate synthase (SPS) and sucrose synthase (SUS) as well as changes in their potential products: sucrose, cellulose and starch in the leaves of Miscanthus  ×  giganteus and Zea mays . Low temperature (12–14 °C) increased SPS content in Miscanthus (MG) and chilling-sensitive maize line (Zm-S), but not in chilling-tolerant one (Zm-T). In Zm-S line, chilling also caused the higher intensity of labelling of SPS in the cytoplasm of mesophyll cells, as demonstrated by electron microscopy. SUS labelling was also increased by cold stress only in MG plants what was observed in the secondary wall between mesophyll and bundle sheath cells, as well as in the vacuoles of companion cells. Cold led to a marked increase in total starch grain area in the chloroplasts of Zm-S line. In turn, Fourier transform infrared spectroscopy (FTIR) showed a slight shift in the cellulose band position, which may indicate the formation of more compact cellulose arrangement in Zm-T maize line. In conclusion, this work presents new findings supporting diversified cold-response, not only between two C 4 plant species but also within one species of maize.

Stipa purpurea, an endemic forage species on the Tibetan Plateau, is highly resistant to cold and drought, but the mechanisms underlying its responses to drought stress remain elusive. An understanding of such mechanisms may be useful for developing cultivars that are adaptable to water deficit. In this study, we analyzed the physiological and proteomic responses of S. purpurea under increasing drought stress. Seedlings of S. purpurea were subjected to a drought gradient in a controlled experiment, and proteins showing changes in abundance under these conditions were identified by two-dimensional electrophoresis followed by mass spectrometry analysis. A western blotting analysis was conducted to confirm the increased abundance of a heat-shock protein, NCED2, and a dehydrin in S. purpurea seedlings under drought conditions. We detected carbonylated proteins to identify oxidation-sensitive proteins in S. purpurea seedlings, and found that ribulose-1, 5-bisphosphate carboxylase oxygenase (RuBisCO) was one of the oxidation-sensitive proteins under drought. Together, these results indicated drought stress might inhibit photosynthesis in S. purpurea by oxidizing RuBisCO, but the plants were able to maintain photosynthetic efficiency by a compensatory upregulation of unoxidized RuBisCO and other photosynthesis-related proteins. Further analyses confirmed that increased abundance of antioxidant enzymes could balance the redox status of the plants to mitigate drought-induced oxidative damage.

C4 photosynthesis has evolved more than 60 times as a carbon-concentrating mechanism to augment the ancestral C3 photosynthetic pathway. The rate and the efficiency of photosynthesis are greater in the C4 than C3 type under atmospheric CO2 depletion, high light and temperature, suggesting these factors as important selective agents. This hypothesis is consistent with comparative analyses of grasses, which indicate repeated evolutionary transitions from shaded forest to open habitats. However, such environmental transitions also impact strongly on plant–water relations. We hypothesize that excessive demand for water transport associated with low CO2, high light and temperature would have selected for C4 photosynthesis not only to increase the efficiency and rate of photosynthesis, but also as a water-conserving mechanism. Our proposal is supported by evidence from the literature and physiological models. The C4 pathway allows high rates of photosynthesis at low stomatal conductance, even given low atmospheric CO2. The resultant decrease in transpiration protects the hydraulic system, allowing stomata to remain open and photosynthesis to be sustained for longer under drying atmospheric and soil conditions. The evolution of C4 photosynthesis therefore simultaneously improved plant carbon and water relations, conferring strong benefits as atmospheric CO2 declined and ecological demand for water rose.

Multiple-herbicide resistance (MHR) in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum) is a global problem leading to a loss of chemical weed control in cereal crops. Although poorly understood, in common with multiple-drug resistance (MDR) in tumors, MHR is associated with an enhanced ability to detoxify xenobiotics. In humans, MDR is linked to the overexpression of a pi class glutathione transferase (GSTP1), which has both detoxification and signaling functions in promoting drug resistance. In both annual rye-grass and black-grass, MHR was also associated with the increased expression of an evolutionarily distinct plant phi (F) GSTF1 that had a restricted ability to detoxify herbicides. When the black-grass A. myosuroides (Am) Am GSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides and showed similar changes in their secondary, xenobiotic, and antioxidant metabolism to those determined in MHR weeds. Transcriptome array experiments showed that these changes in biochemistry were not due to changes in gene expression. Rather, Am GSTF1 exerted a direct regulatory control on metabolism that led to an accumulation of protective flavonoids. Further evidence for a key role for this protein in MHR was obtained by showing that the GSTP1- and MDR-inhibiting pharmacophore 4-chloro-7-nitro-benzoxadiazole was also active toward Am GSTF1 and helped restore herbicide control in MHR black-grass. These studies demonstrate a central role for specific GSTFs in MHR in weeds that has parallels with similar roles for unrelated GSTs in MDR in humans and shows their potential as targets for chemical intervention in resistant weed management.

As a consequence of the tight linkages among soils, plants and microbes inhabiting the rhizosphere, we hypothesized that soil nutrient and microbial stoichiometry would differ among plant species and be correlated within plant rhizospheres. We assessed plant tissue carbon (C) : nitrogen (N) : phosphorus (P) ratios for eight species representing four different plant functional groups in a semiarid grassland during near-peak biomass. Using intact plant species-specific rhizospheres, we examined soil C : N : P, microbial biomass C : N, and soil enzyme C : N : P nutrient acquisition activities. We found that few of the plant species' rhizospheres demonstrated distinct stoichiometric properties from other plant species and unvegetated soil. Plant tissue nutrient ratios and components of below-ground rhizosphere stoichiometry predominantly differed between the C4 plant species Buchloe dactyloides and the legume Astragalus laxmannii. The rhizospheres under the C4 grass B. dactyloides exhibited relatively higher microbial C and lower soil N, indicative of distinct soil organic matter (SOM) decomposition and nutrient mineralization activities. Assessing the ecological stoichiometry among plant species' rhizospheres is a high-resolution tool useful for linking plant community composition to below-ground soil microbial and nutrient characteristics. By identifying how rhizospheres differ among plant species, we can better assess how plant–microbial interactions associated with ecosystem-level processes may be influenced by plant community shifts.

Powdery mildew resistance gene Pm21, located on the chromosome 6V short arm of Haynaldia villosa and transferred to wheat as a 6VS·6AL translocation (T6VS·6AL), confers durable and broad-spectrum resistance to wheat powdery mildew. Pm21 has become a key gene resource for powdery mildew resistance breeding all over the world. In China, 12 wheat varieties containing Pm21 have been planted on more than 3.4 million hectares since 2002. Pm21 has been intractable to molecular genetic mapping because the 6VS does not pair and recombine with the 6AS. Moreover, all known accessions of H. villosa are immune to powdery mildew fungus. Pm21 is still defined by cytogenetics as a locus. In the present study, a putative serine and threonine protein kinase gene Stpk-V was cloned and characterized with an integrative strategy of molecular and cytogenetic techniques. Stpk-V is located on the Pm21 locus. The results of a single cell transient expression assay showed that Stpk-V could decrease the haustorium index dramatically. After the Stpk-V was transformed into a susceptible wheat variety Yangmai158, the characterized transgenic plants showed high and broad-spectrum powdery mildew resistance similar to T6VS·6AL. Silencing of the Stpk-V by virus-induced gene silencing in both T6VS·6AL and H. villosa resulted in their increased susceptibility. Stpk-V could be induced by Bgt and exogenous H₂O₂, but it also mediated the increase of endogenous H₂O₂, leading to cell death and plant resistance when the plant was attacked by Bgt.

C₄ photosynthesis affords higher photosynthetic carbon conversion efficiency than C₃ photosynthesis and it therefore represents an attractive target for engineering efforts aiming to improve crop productivity. To this end, blueprints are required that reflect C₄ metabolism as closely as possible. Such blueprints have been derived from comparative transcriptome analyses of C₃ species with related C₄ species belonging to the NAD-malic enzyme (NAD-ME) and NADP-ME subgroups of C₄ photosynthesis. However, a comparison between C₃ and the phosphoenolpyruvate carboxykinase (PEP-CK) subtype of C₄ photosynthesis is still missing. An integrative analysis of all three C₄ subtypes has also not been possible to date, since no comparison has been available for closely related C₃ and PEP-CK C₄ species. To generate the data, the guinea grass Megathyrsus maximus, which represents a PEP-CK species, was analysed in comparison with a closely related C₃ sister species, Dichanthelium clandestinum, and with publicly available sets of RNA-Seq data from C₄ species belonging to the NAD-ME and NADP-ME subgroups. The data indicate that the core C₄ cycle of the PEP-CK grass M. maximus is quite similar to that of NAD-ME species with only a few exceptions, such as the subcellular location of transfer acid production and the degree and pattern of up-regulation of genes encoding C₄ enzymes. One additional mitochondrial transporter protein was associated with the core cycle. The broad comparison identified sucrose and starch synthesis, as well as the prevention of leakage of C₄ cycle intermediates to other metabolic pathways, as critical components of C₄ metabolism. Estimation of intercellular transport fluxes indicated that flux between cells is increased by at least two orders of magnitude in C₄ species compared with C₃ species. In contrast to NAD-ME and NADP-ME species, the transcription of photosynthetic electron transfer proteins was unchanged in PEP-CK. In summary, the PEP-CK blueprint of M. maximus appears to be simpler than those of NAD-ME and NADP-ME plants.

Many herbicide-resistant weed species are polyploids, but far too little about the evolution of resistance mutations in polyploids is understood. Hexaploid wild oat (Avena fatua) is a global crop weed and many populations have evolved herbicide resistance. We studied plastidic acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide resistance in hexaploid wild oat and revealed that resistant individuals can express one, two or three different plastidic ACCase gene resistance mutations (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg). Using ACCase resistance mutations as molecular markers, combined with genetic, molecular and biochemical approaches, we found in individual resistant wild-oat plants that (1) up to three unlinked ACCase gene loci assort independently following Mendelian laws for disomic inheritance, (2) all three of these homoeologous ACCase genes were transcribed, with each able to carry its own mutation and (3) in a hexaploid background, each individual ACCase resistance mutation confers relatively low-level herbicide resistance, in contrast to high-level resistance conferred by the same mutations in unrelated diploid weed species of the Poaceae (grass) family. Low resistance conferred by individual ACCase resistance mutations is likely due to a dilution effect by susceptible ACCase expressed by homoeologs in hexaploid wild oat and/or differential expression of homoeologous ACCase gene copies. Thus, polyploidy in hexaploid wild oat may slow resistance evolution. Evidence of coexisting non-target-site resistance mechanisms among wild-oat populations was also revealed. In all, these results demonstrate that herbicide resistance and its evolution can be more complex in hexaploid wild oat than in unrelated diploid grass weeds. Our data provide a starting point for the daunting task of understanding resistance evolution in polyploids.

Changing climatic scenarios affect plant growth and consequences are more malicious in drought conditions. This study was performed for better understanding of tolerance mechanisms under prevailing drought stress and succeeding recovery in Axonopus compressus by exogenously applied abscisic acid (ABA) and glycine betaine (GB). Three A. compressus accessions (A-38, A-58 and A-59) were subjected to well-watered (100% field capacity) and drought (40% field capacity) conditions. Two weeks later, plants were recovered from drought by re-watering. Water (control), GB, ABA and their combination were foliar applied on plants under drought twice a week until recovery. Drought stress decreased photosynthetic pigments and increased reactive oxygen species, lipid peroxidation, osmolytes and antioxidants in all accessions of A. compressus . Nonetheless, exogenous ABA and GB alone or in combination improved drought tolerance in all accessions which was maintained even after recovery. Maximum decrease in hydrogen peroxide and malondialdehyde, and increase in soluble sugars, proteins, proline, phenolics and chlorophyll contents, and superoxide dismutase, catalase, peroxidase and ascorbate peroxidase activity was recorded when GB was applied alone under drought. Order of improvement in drought tolerance among accessions was A-58 > A-59 > A-38. In conclusion, improved drought tolerance mechanisms by ABA and GB in A. compressus were retained even after recovery.